using AcDream.App.Rendering;

namespace AcDream.App.Tests.Rendering;

public sealed class GlTextureOwnershipTests
{
    [Fact]
    public void ConstructionRollbackDeletesAllNamesInReverseOrder()
    {
        var api = new FakeTextureNameApi();
        var transaction = new GlTextureConstructionTransaction(api);

        Assert.Equal(1u, transaction.Allocate());
        Assert.Equal(2u, transaction.Allocate());
        Assert.Equal(3u, transaction.Allocate());

        transaction.Rollback();
        transaction.Rollback();

        Assert.Equal([3u, 2u, 1u], api.DeleteAttempts);
    }

    [Fact]
    public void ConstructionRollbackAttemptsEveryNameAndReportsFailures()
    {
        var api = new FakeTextureNameApi { FailingDelete = 2 };
        var transaction = new GlTextureConstructionTransaction(api);
        _ = transaction.Allocate();
        _ = transaction.Allocate();
        _ = transaction.Allocate();

        AggregateException failure = Assert.Throws<AggregateException>(transaction.Rollback);

        Assert.Single(failure.InnerExceptions);
        Assert.Equal([3u, 2u, 1u], api.DeleteAttempts);
        Assert.Equal([3u, 1u], api.Deleted);

        api.FailingDelete = null;
        transaction.RetryCleanup();

        Assert.True(transaction.IsCleanupComplete);
        Assert.Equal([3u, 2u, 1u, 2u], api.DeleteAttempts);
        Assert.Equal([3u, 1u, 2u], api.Deleted);
    }

    [Fact]
    public void CommittedNamesAreNeverDeletedByConstructionTransaction()
    {
        var api = new FakeTextureNameApi();
        var transaction = new GlTextureConstructionTransaction(api);
        _ = transaction.Allocate();
        _ = transaction.Allocate();

        transaction.Commit();
        transaction.Rollback();

        Assert.Empty(api.DeleteAttempts);
        Assert.Throws<InvalidOperationException>(() => transaction.Allocate());
    }

    [Fact]
    public void TrackedTextureUploadFailureLeavesEveryActualBranchNameInTransaction()
    {
        var api = new FakeTextureNameApi();
        var transaction = new GlTextureConstructionTransaction(api);
        uint first = TrackedTextureConstruction.Create(transaction, _ => { });

        Assert.Throws<InvalidOperationException>(() =>
            TrackedTextureConstruction.Create(
                transaction,
                _ => throw new InvalidOperationException("upload failed")));
        transaction.Rollback();

        Assert.Equal(1u, first);
        Assert.Equal([2u, 1u], api.DeleteAttempts);
    }

    [Fact]
    public void TerrainAtlasRoutesEveryTerrainAlphaAndFallbackUploadThroughTracker()
    {
        string source = File.ReadAllText(Path.Combine(
            FindRepoRoot(),
            "src",
            "AcDream.App",
            "Rendering",
            "TerrainAtlas.cs"));

        Assert.Equal(5, CountOccurrences(source, "TrackedTextureConstruction.Create("));
        Assert.Equal(
            5,
            System.Text.RegularExpressions.Regex.Matches(
                source,
                "TrackedTextureConstruction\\.Create\\(\\s*textures,\\s*gl,\\s*\\\"").Count);
        Assert.DoesNotContain("textures.Allocate()", source, StringComparison.Ordinal);
    }

    [Fact]
    public void ProductionGlResourcePathsUseAlwaysOnCheckedCommitBoundaries()
    {
        string root = FindRepoRoot();
        string textureNames = File.ReadAllText(Path.Combine(
            root, "src", "AcDream.App", "Rendering", "GlTextureConstructionTransaction.cs"));
        string shaderPrograms = File.ReadAllText(Path.Combine(
            root, "src", "AcDream.App", "Rendering", "ShaderProgramConstruction.cs"));
        string terrain = File.ReadAllText(Path.Combine(
            root, "src", "AcDream.App", "Rendering", "TerrainAtlas.cs"));
        string text = File.ReadAllText(Path.Combine(
            root, "src", "AcDream.App", "Rendering", "TextRenderer.cs"));
        string bindless = File.ReadAllText(Path.Combine(
            root, "src", "AcDream.App", "Rendering", "Wb", "BindlessSupport.cs"));

        Assert.Contains("GlResourceCommand.CreateTexture", textureNames, StringComparison.Ordinal);
        Assert.Contains("GlResourceCommand.DeleteTexture", textureNames, StringComparison.Ordinal);
        Assert.Contains("GlResourceCommand.CreateName", shaderPrograms, StringComparison.Ordinal);
        Assert.Contains("GlResourceCommand.DeleteShader", shaderPrograms, StringComparison.Ordinal);
        Assert.Contains("GlResourceCommand.DeleteProgram", shaderPrograms, StringComparison.Ordinal);
        Assert.Contains("_anisotropyBindingMutation.Execute", terrain, StringComparison.Ordinal);
        Assert.Contains("GlResourceCommand.DeleteTexture", terrain, StringComparison.Ordinal);
        Assert.Contains("GlResourceCommand.CreateTexture", text, StringComparison.Ordinal);
        Assert.Contains("GlResourceCommand.Execute", text, StringComparison.Ordinal);
        Assert.Contains("make bindless handle", bindless, StringComparison.Ordinal);
        Assert.Contains("GlResourceCommand.Execute", bindless, StringComparison.Ordinal);
    }

    [Fact]
    public void SecondBindlessAcquireFailureRollsBackFirstHandle()
    {
        var residency = new FakeResidency { FailingAcquireTexture = 20 };
        var pair = new BindlessTexturePair(10, 20, residency.Acquire, residency.Release);

        Assert.Throws<InvalidOperationException>(() => pair.Acquire());

        Assert.False(pair.IsFullyResident);
        Assert.Equal([10u, 20u], residency.AcquireAttempts);
        Assert.Equal([1010ul], residency.ReleaseAttempts);
    }

    [Fact]
    public void FailedPrefixRollbackRemainsOwnedAndRetryDoesNotReacquireIt()
    {
        var residency = new FakeResidency
        {
            FailingAcquireTexture = 20,
            FailingReleaseHandle = 1010,
        };
        var pair = new BindlessTexturePair(10, 20, residency.Acquire, residency.Release);

        Assert.Throws<AggregateException>(() => pair.Acquire());
        residency.FailingAcquireTexture = null;
        residency.FailingReleaseHandle = null;

        Assert.Equal((1010ul, 1020ul), pair.Acquire());

        Assert.True(pair.IsFullyResident);
        Assert.Equal([10u, 20u, 20u], residency.AcquireAttempts);
        Assert.Equal([1010ul], residency.ReleaseAttempts);
    }

    [Fact]
    public void BindlessReleaseAttemptsBothAndRetriesOnlyPendingHandle()
    {
        var residency = new FakeResidency();
        var pair = new BindlessTexturePair(10, 20, residency.Acquire, residency.Release);
        _ = pair.Acquire();
        residency.FailingReleaseHandle = 1010;

        Assert.Throws<AggregateException>(pair.Release);
        Assert.False(pair.IsFullyResident);
        Assert.True(pair.HasAnyResident);
        Assert.Equal([1010ul, 1020ul], residency.ReleaseAttempts);

        residency.FailingReleaseHandle = null;
        pair.Release();
        pair.Release();

        Assert.False(pair.HasAnyResident);
        Assert.Equal([1010ul, 1020ul, 1010ul], residency.ReleaseAttempts);
    }

    [Fact]
    public void MutationFailureStillRestoresThePreviouslyResidentPair()
    {
        var residency = new FakeResidency();
        var pair = new BindlessTexturePair(10, 20, residency.Acquire, residency.Release);
        var guard = new BindlessTextureMutationGuard(pair);
        _ = pair.Acquire();

        Assert.Throws<InvalidOperationException>(() =>
            guard.Execute(() => throw new InvalidOperationException("mutation failed")));

        Assert.True(pair.IsFullyResident);
        Assert.False(guard.RestoreRequired);
        Assert.Equal([10u, 20u, 10u, 20u], residency.AcquireAttempts);
    }

    [Fact]
    public void FailedReacquireKeepsRestoreIntentUntilALaterMutationRetry()
    {
        var residency = new FakeResidency();
        var pair = new BindlessTexturePair(10, 20, residency.Acquire, residency.Release);
        var guard = new BindlessTextureMutationGuard(pair);
        _ = pair.Acquire();
        residency.FailingAcquireTexture = 20;

        Assert.Throws<InvalidOperationException>(() => guard.Execute(() => { }));
        Assert.True(guard.RestoreRequired);
        Assert.False(pair.HasAnyResident);

        residency.FailingAcquireTexture = null;
        guard.Execute(() => { });

        Assert.False(guard.RestoreRequired);
        Assert.True(pair.IsFullyResident);
        Assert.Equal([10u, 20u, 10u, 20u, 10u, 20u], residency.AcquireAttempts);
    }

    [Fact]
    public void PartialReleaseFailurePreventsMutationAndRestoresPairBeforeThrowing()
    {
        var residency = new FakeResidency();
        var pair = new BindlessTexturePair(10, 20, residency.Acquire, residency.Release);
        var guard = new BindlessTextureMutationGuard(pair);
        _ = pair.Acquire();
        residency.FailingReleaseHandle = 1010;
        int mutations = 0;

        Assert.Throws<AggregateException>(() => guard.Execute(() => mutations++));

        Assert.Equal(0, mutations);
        Assert.True(pair.IsFullyResident);
        Assert.False(guard.RestoreRequired);
    }

    [Fact]
    public void FailedTextureMutationRestoresTheExactPriorBinding()
    {
        var bindings = new List<uint>();
        var owner = new RestoredTextureBindingMutation();

        InvalidOperationException failure = Assert.Throws<InvalidOperationException>(() =>
            owner.Execute(
                () => 77,
                bindings.Add,
                42,
                () => throw new InvalidOperationException("mutation failed")));

        Assert.Equal("mutation failed", failure.Message);
        Assert.Equal([42u, 77u], bindings);
    }

    [Fact]
    public void TextureMutationReportsBothMutationAndBindingRestoreFailure()
    {
        int bindCalls = 0;
        var owner = new RestoredTextureBindingMutation();

        AggregateException failure = Assert.Throws<AggregateException>(() =>
            owner.Execute(
                () => 77,
                _ =>
                {
                    bindCalls++;
                    if (bindCalls == 2)
                        throw new InvalidOperationException("restore failed");
                },
                42,
                () => throw new InvalidOperationException("mutation failed")));

        Assert.Equal(2, failure.InnerExceptions.Count);
        Assert.Equal(2, bindCalls);
        Assert.True(owner.HasPendingRestore);
    }

    [Fact]
    public void FailedBindingRestoreRetriesTheOriginalBindingBeforeAnotherMutation()
    {
        var owner = new RestoredTextureBindingMutation();
        var bindings = new List<uint>();
        int restoreFailures = 1;
        int mutations = 0;

        Assert.Throws<InvalidOperationException>(() =>
            owner.Execute(
                () => 77,
                binding =>
                {
                    bindings.Add(binding);
                    if (binding == 77 && restoreFailures-- > 0)
                        throw new InvalidOperationException("restore failed");
                },
                42,
                () => mutations++));

        Assert.True(owner.HasPendingRestore);
        owner.Execute(
            () => 77,
            bindings.Add,
            42,
            () => mutations++);

        Assert.False(owner.HasPendingRestore);
        Assert.Equal([42u, 77u, 77u, 42u, 77u], bindings);
        Assert.Equal(2, mutations);
    }

    [Fact]
    public void ConstructionCleanupLedgerRetainsNestedFailureUntilRetryCompletes()
    {
        var api = new FakeTextureNameApi { FailingDelete = 1 };
        var transaction = new GlTextureConstructionTransaction(api);
        _ = transaction.Allocate();
        AggregateException cleanupFailure = Assert.Throws<AggregateException>(
            transaction.Rollback);
        var constructionFailure = new GlResourceConstructionException(
            "synthetic construction failure",
            transaction,
            [new InvalidOperationException("build failed"), cleanupFailure]);
        var ledger = new GlConstructionCleanupLedger();

        Assert.True(ledger.RetainFrom(constructionFailure));
        Assert.Throws<AggregateException>(ledger.Dispose);
        Assert.False(ledger.IsComplete);

        api.FailingDelete = null;
        ledger.Dispose();

        Assert.True(ledger.IsComplete);
        Assert.True(constructionFailure.IsCleanupComplete);
    }

    private sealed class FakeTextureNameApi : IGlTextureNameApi
    {
        private uint _nextName = 1;

        public uint? FailingDelete { get; set; }
        public List<uint> DeleteAttempts { get; } = [];
        public List<uint> Deleted { get; } = [];

        public uint GenTexture() => _nextName++;

        public void DeleteTexture(uint texture)
        {
            DeleteAttempts.Add(texture);
            if (FailingDelete == texture)
                throw new InvalidOperationException("delete failed");
            Deleted.Add(texture);
        }
    }

    private static int CountOccurrences(string source, string value)
    {
        int count = 0;
        int cursor = 0;
        while ((cursor = source.IndexOf(value, cursor, StringComparison.Ordinal)) >= 0)
        {
            count++;
            cursor += value.Length;
        }
        return count;
    }

    private static string FindRepoRoot()
    {
        DirectoryInfo? directory = new(AppContext.BaseDirectory);
        while (directory is not null)
        {
            if (File.Exists(Path.Combine(directory.FullName, "AcDream.slnx")))
                return directory.FullName;
            directory = directory.Parent;
        }
        throw new DirectoryNotFoundException("Could not find AcDream.slnx.");
    }

    private sealed class FakeResidency
    {
        public uint? FailingAcquireTexture { get; set; }
        public ulong? FailingReleaseHandle { get; set; }
        public List<uint> AcquireAttempts { get; } = [];
        public List<ulong> ReleaseAttempts { get; } = [];

        public ulong Acquire(uint texture)
        {
            AcquireAttempts.Add(texture);
            if (FailingAcquireTexture == texture)
                throw new InvalidOperationException("acquire failed");
            return 1000ul + texture;
        }

        public void Release(ulong handle)
        {
            ReleaseAttempts.Add(handle);
            if (FailingReleaseHandle == handle)
                throw new InvalidOperationException("release failed");
        }
    }
}